The present invention relates to a cleaning method suitable for removing contamination from a vacuum vapor deposition tank and the like which constitute a vacuum vapor deposition apparatus used in the manufacture of, for instance, a magnetic recording medium, and to a cleaning apparatus for implementing the cleaning method.
As is generally known, magnetic disks and magnetic tapes are used extensively as magnetic recording media for recording video signals and audio signals. The magnetic recording media are formed by applying or vapor-depositing a magnetic material onto the surface of a substrate in which a polyester such as polyethylene terephthalate or a polyolefin such as polypropylene is formed on a film.
With respect to the magnetic recording media, there has been an increasing demand for the higher-density recording of signals. To cope with this demand, improvements on the magnetic layer are required, including the higher density of the magnetic material in the magnetic layer, an increase in coercive force, the shift of the frequency characteristic toward the short-wavelength side, and the production of a thinner film for the magnetic layer.
However, in the case where the magnetic layer is formed on the substrate surface by being applied thereto, a binder in principle remains in the magnetic layer, so that it is extremely difficult to satisfy various conditions required for the aforementioned higher-density recording.
To overcome such problems, methods of manufacturing magnetic recording media through vapor deposition processes, including vacuum vapor deposition, sputtering, ion plating, and the like have been proposed.
The manufacture of magnetic recording media through vacuum vapor deposition is effected by using a vacuum vapor deposition apparatus arranged as shown in FIG. 5. It should be noted that FIG. 5 is a schematic perspective view illustrating only a portion of the vacuum vapor deposition apparatus. A vacuum vapor deposition apparatus 1 is comprised of a cylindrical main cooling drum 2 which is rotatably disposed in an unillustrated vacuum tank; pass rollers 4, 5 for transporting a film-like base 3 in a state in which the base 3 is wound around the peripheral surface of the main cooling drum 2; a crucible 7 accommodating a magnetic material 6 and disposed on the lower side of the main cooling drum 2; an electron gun 8 for heating and evaporating the magnetic material 6 by irradiating the magnetic material 6 with an electron beam; a condensate hood 9 for preventing the evaporated magnetic material from adhering to objects other than the film; a mask 10 for restricting an evaporation area of the magnetic material 6, and so on.
In addition, the interior of the vacuum tank is held at, for example, 1.0 10.sup.-4 [Torr] by means of a vacuum exhaust pump. In addition, the arrangement provided is such that the base 3 is passed from an unillustrated feed roller to the pass roller 4, is wound around the peripheral surface of the cooling roller 2, and is taken up onto an unillustrated takeup roller via the pass roller 5.
An opening 10a and a shutter mechanism are provided in the mask 10 at a position facing the peripheral surface of the main cooling drum 2, so as to allow both ends of the base 3 to be shielded and the evaporation area to be restricted, as required, when the magnetic material 6 is vapor-deposited.
Next, a description will be given of a method of manufacturing a magnetic recording medium by using the above-described apparatus 1. The feed roller is driven to convey the base 3, and the main cooling drum 2 is rotated in the direction of arrow A in a state in which the main cooling drum 2 is cooled to, for example, -30.degree. C. or thereabouts.
At the same time, the magnetic material 6 is evaporated by being heated by an electron beam from the electron gun 8, and evaporated particles (magnetic material) are allowed to be continuously vapor-deposited onto the surface of the base 3 exposed at the opening 10a. In this manner, the magnetic material 6 is vapor-deposited onto the surface of the base 3, and the vapor-deposited base 3 is taken up onto the takeup roller via the pass roller 5.
As compared with the magnetic recording medium manufactured by coating with the magnetic material, the magnetic recording medium thus manufactured provides a remarkably large reproduction output, and the frequency characteristic in magnetic recording extends to the shorter-wavelength side. Hence, the magnetic recording medium of this type is useful as a high-density magnetic recording medium.
The vacuum vapor deposition on the base 3 is effected continuously with respect to a base having a length of several thousand meters. If continuous vapor deposition is effected with respect to such an elongated base, the residue of the evaporated particles adheres in a large volume to the shutter mechanism including the mask 10 and to internal walls of the condensate hood 9. If the amount of the adhering residue becomes large, there arise such problems as the peeling off the residue from the inner walls, the impairment of the restriction of the aforementioned evaporation area, and the adsorption of gas components in the atmospheric air. For this reason, it has been necessary to remove the residue for each vapor deposition process or replace the members with new ones.
Conventionally, the removal of the residue is carried out manually by using a jig. However, since the residue adheres firmly to the members, it is necessary to break it off or scrape it off, so that the cleaning operation has been troublesome and required much labor. Although careful cleaning of the residue ensures stabilization of the quality of the magnetic recording medium, the need for expending much time in the cleaning operation disadvantageously prolongs the cycle of the vapor deposition process, resulting in a substantial decline in productivity.
Furthermore, most of the removed residue has hitherto been discarded. Since the members to which the residue adheres are conventionally damaged or scraped by means of the scraping jig when the residue is scraped off, as described above, the removed residue includes impurities such as scraped pieces of the members, which causes a hindrance at the time of collection and separation of the residue for reutilization, and has constituted a major factor of a decline in the utilization efficiency of the magnetic material.